This invention relates to munitions, and, more particularly, to a projectile system that can be fired from air against underwater objects located at moderate underwater ranges.
Projectiles are widely used against targets in air. In the most common approach, the projectile is placed into a gun, together with a propellant. The propellant is ignited, driving the projectile out of the barrel of the gun and toward the target.
Projectiles have extremely limited capability to be fired from air against targets in water, primarily for three reasons. First, the trajectory of the projectile can be radically altered when it encounters the interface between the air and the water (i.e., the surface of the water). At a shallow angle of incidence to the water, the projectile may not enter the water at all, and instead may skip away. At a higher angle of incidence to the water, the projectile may enter the water but its path is altered. This problem is always a consideration, but it is of particular concern to the accuracy of the projectile when the surface of the water exhibits a constantly varying state due to wave motion. Second, the drag produced by the water rapidly slows the projectile and drastically limits its range. The range of conventional projectiles in water varies according to the weight and initial velocity of the projectile, but is typically at most no more than about 3 feet under optimal conditions for a conventional 20 millimeter projectile. Third, the lateral hydrodynamic forces on the projectile can cause it to tumble, further limiting its range and effectiveness.
For these reasons, projectiles are seldom fired from air against targets submerged in water. If conventional projectiles are fired from air toward a target submerged in water, they are largely ineffective. Instead, self-propelled devices such as torpedoes are used, and even in this case the torpedo is usually dropped into the water before its propulsion is started.
There are applications where a projectile that can be fired against underwater targets from the air would be useful. For example, a standard defense against amphibious military operations is underwater mines placed at moderate depths in near-shore landing areas. Such mines are now removed by specially trained swimmers at considerable risk or robotic devices which have significant constraints in their operation. An alternative approach would be to fire a projectile at the underwater mine from the air, as from a helicopter. Projectiles are far less costly than self-propelled devices in such applications, and could be made of different sizes and types for firing from a range of weapons of both small and large bores.
Thus, there is a need for a projectile that can be fired from air against underwater targets. The present invention fulfills this need, and further provides related advantages.